modelCrossHX
Information
Model CrossHX represent the model of a cross flow plate heat exchanger where air is used as secondary fluid. Pressure drop is taken into account in the air side. It is based on the connection of different sub-components:
- A Flow1Dim component representing the flow of the fluid in one side of the exchanger
- A MultiFlow1D component representing the flow of air in the other side of the exchanger
- A MetalWall component representing the thermal energy accumulation in the metal wall
Modelling options
In the Initialization tab the following options are availabe:
- steadystate_wf: if true, the derivative of enthalpy of the working fluid is set to zero during Initialization
- steadystate_T_wall: if true, the derivative of temperature of the metal wall is set to zero during Initialization
- constinit_sf: if true, the pressure drop in the air side is set to a constant value during Initialization
- UseHomotopy_sf: if true, it uses homotopy to set the pressure drop to zero during Initialization
Numerical options
The numerical options available for the CrossHX are the one implemented in Cell1Dim.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Integer | N | 5 | Number of cells |
| Modelica.SIunits.Volume | V_wf | 0.0397 | Volume of working fluid side |
| Modelica.SIunits.Area | A_wf | 16.18 | Lateral surface of working fluid side |
| Modelica.SIunits.Volume | V_sf | 0.0397 | Total volume of fluid |
| Modelica.SIunits.Area | A_sf | 16.18 | Total Lateral surface |
| Modelica.SIunits.MassFlowRate | Mdotnom_wf | 0.2588 | Nominal fluid flow rate |
| Modelica.SIunits.MassFlowRate | Mdotnom_sf | 3 | Nominal fluid flow rate |
| Modelica.SIunits.Mass | M_wall_tot | 69 | Mass of the Wall |
| Modelica.SIunits.SpecificHeatCapacity | c_wall | 500 | Specific heat capacity of the metal |
| General › Heat transfer | |||
| Modelica.SIunits.CoefficientOfHeatTransfer | Unom_l | 300 | if HTtype = LiqVap : Heat transfer coefficient, liquid zone |
| Modelica.SIunits.CoefficientOfHeatTransfer | Unom_tp | 700 | if HTtype = LiqVap : heat transfer coefficient, two-phase zone |
| Modelica.SIunits.CoefficientOfHeatTransfer | Unom_v | 400 | if HTtype = LiqVap : heat transfer coefficient, vapor zone |
| Modelica.SIunits.CoefficientOfHeatTransfer | Unom_sf | 100 | Constant heat transfer coefficient |
| General › Pdrop_sf | |||
| Boolean | UseNom_sf | false | Use Nominal conditions to compute pressure drop characteristics |
| Modelica.SIunits.Length | h_sf | 0 | Static fluid head (dp = h * rho * g) |
| Real | k_sf | 38.4E3*9.5 | Coefficient for linear pressure drop (dp = k * V_dot) |
| Modelica.SIunits.Area | Athroat_sf | (2*9.5*23282.7)^(-0.5) | Valve throat area for quadratic pressure drop (dp = 1/A?*M_dot?/(2*rho)) |
| Modelica.SIunits.Pressure | DELTAp_0_sf | 500 | Pressure drop below which a 3rd order interpolation is used for the computation of the flow rate in order to avoid infinite derivative at 0 |
| Nominal Conditions › Pdrop_sf | |||
| Modelica.SIunits.Pressure | p_nom_sf | 1e5 | Nominal pressure |
| Modelica.SIunits.Temperature | T_nom_sf | 283.15 | Nominal temperature |
| Modelica.SIunits.Density | rho_nom_sf | Medium1.density_pT(p_nom_sf, T_nom_sf) | Nominal density |
| Modelica.SIunits.Pressure | DELTAp_stat_nom_sf | 0 | Nominal static pressure drop |
| Modelica.SIunits.Pressure | DELTAp_lin_nom_sf | 0 | Nominal linear pressure drop |
| Modelica.SIunits.Pressure | DELTAp_quad_nom_sf | 0 | Nominal quadratic pressure drop |
| Boolean | use_rho_nom_sf | false | Use the nominal density for the computation of the pressure drop (i.e it depends only the flow rate) |
| Initialization | |||
| Modelica.SIunits.Pressure | pstart_wf | 23.57 | Fluid pressure start value |
| Medium1.Temperature | Tstart_wf_in | Inlet temperature start value | |
| Medium1.SpecificEnthalpy | hstart_wf_in | Medium1.specificEnthalpy_pT(pstart_wf, Tstart_wf_in) | Start value of inlet enthalpy |
| Modelica.SIunits.Temperature | T_start_wall | (Tstart_wf_in + T_nom_sf)/2 | Start value of temperature (initialized by default) |
| Modelica.SIunits.Time | t_init_sf | 10 | if constinit is true, time during which the pressure drop is set to the constant value DELTAp_start |
| Initialization › Intialization options | |||
| Boolean | steadystate_wf | true | if true, sets the derivative of h (working fluids enthalpy in each cell) to zero during Initialization |
| Boolean | steadystate_T_wall | true | if true, sets the derivative of T_wall to zero during Initialization |
| Boolean | constinit_sf | false | if true, sets the pressure drop to a constant value at the beginning of the simulation in order to avoid oscillations |
| Boolean | UseHomotopy_sf | false | if true, uses homotopy to set the pressure drop to zero in the first initialization |
| Modelica.SIunits.Pressure | DELTAp_start_sf | DELTAp_stat_nom_sf + DELTAp_lin_nom_sf + DELTAp_quad_nom_sf | Start Value for the pressure drop |
| Numerical options | |||
| Discretizations | Discretization_wf | ThermoCycle.Functions.Enumerations.Discretizations.centr_diff | Selection of the spatial discretization scheme |
| Boolean | Mdotconst_wf | false | Set to yes to assume constant mass flow rate at each node (easier convergence) |
| Boolean | max_der_wf | false | Set to yes to limit the density derivative during phase transitions |
| Boolean | filter_dMdt_wf | false | Set to yes to filter dMdt with a first-order filter |
| Real | max_drhodt_wf | 100 | Maximum value for the density derivative |
| Modelica.SIunits.Time | TT_wf | 1 | Integration time of the first-order filter |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| ThermoCycle.Interfaces.Fluid.FlangeA | Inlet_fl1 | ||
| ThermoCycle.Interfaces.Fluid.FlangeB | Outlet_fl1 | ||
| ThermoCycle.Interfaces.Fluid.FlangeA | Inlet_fl2 | ||
| ThermoCycle.Interfaces.Fluid.FlangeB | Outlet_fl2 |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| ThermoCycle.Components.FluidFlow.Pipes.MultiFlow1D | multiFlow1D_DP | ||
| ThermoCycle.Components.HeatFlow.Walls.MetalWallL[N] | metalWallCell | ||
| ThermoCycle.Components.FluidFlow.Pipes.Cell1Dim[N] | flow1DimCell |
Contents
| Name | Description |
|---|---|
| Medium1 | |
 Medium2 | |
 Medium2HeatTransferModel | |
| Medium1HeatTransferModel |